Thermal Behavior of Polyethylene Reactor Alloys Polymerized by Ziegler–Natta/Late Transition Metal Hybrid Catalyst

Ahmadjo, Saeid; Dehghani, Samaneh; Zohuri, Gholamhossein; Nejabat, Gholam-Reza; Jafarian, Hamed; Ahmadi, Mostafa; Mortazavi, Seyed Mohammad Mahdi

doi:10.1002/mren.201400024

Cited by 14 publications

(8 citation statements)

References 55 publications

(57 reference statements)

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“…Mülhaupt et al have immobilized two bis(imino)pyridyl Fe catalysts with a half sandwich chromocene for production of polyethylene with very broad, trimodal MWD [30][31][32]. Likewise, Ahmadjo et al [33] have provided polyethylene with multimodal melting peaks using hybrid bis(imino)pyridine Fe/Ziegler-Natta catalysts. Many groups have utilized a-diimine nickel complexes in homogeneous or heterogeneous states in combination with Ziegler-Natta or metallocene catalysts in order to synthesize linear/branched polyethylene blend in one reactor [34][35][36][37].…”

Section: Introductionmentioning

confidence: 97%

Characteristics of linear/branched polyethylene reactor blends synthesized by metallocene/late transitional metal hybrid catalysts

Mortazavi

Jafarian

Ahmadi

et al. 2015

J Therm Anal Calorim

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Nickel diimine late transition metal (LTM) and Cp 2 TiCl 2 metallocene catalysts were supported on the TIBA-modified MgCl 2 ÁnEtOH adduct, separately and concurrently, at different ratios, to yield hybrid catalysts, where the catalytic precursors were activated in the ethylene polymerization with TEA as the cocatalyst. Polymerization activities revealed that supported LTM catalysts show very high levels of activity, in an adverse trend with polymerization temperature ranging from 30 to 70°C, in opposition to the activity of metallocene component. Consequently, the proportion of corresponding polymer fractions were tuned by changing reaction temperature as well as catalyst composition. Study of thermal properties confirmed that LTM component is responsible for production of less crystallizable branched chains, while metallocene fraction makes highly crystallizable linear chains. All samples showed noticeable thermorheological complexity due to coexistence of linear and branched microstructures. Interestingly, it was found that increase in metallocene fraction of the hybrid catalyst stalls the terminal relaxation of the produced polymers and increases the entanglement density by decreasing the extent of branching. Study of dynamic mechanical properties revealed that the intensity of b transition could be correlated with the branching level and catalyst composition accordingly.

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Section: Introductionmentioning

confidence: 97%

Characteristics of linear/branched polyethylene reactor blends synthesized by metallocene/late transitional metal hybrid catalysts

Mortazavi

Jafarian

Ahmadi

et al. 2015

J Therm Anal Calorim

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“… The microstructure of polymers determines properties and applications of final products which in turn depend on the polymerization conditions like concentration of the cocatalyst, polymerization temperature, and monomer concentrations. The objective of this work is to synthesize poly(1‐hexene) as a PO with desired molecular weights for DRA application. To the best of our knowledge, the role of polymerization parameters and product characteristics on drag reduction efficiency of poly α‐olefins is not studied extensively.…”

Section: Introductionmentioning

confidence: 99%

Preparation of ultra high molecular weight amorphous poly(1-hexene) by a Ziegler-Natta catalyst

Ahmadjo

2016

Polym. Adv. Technol.

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High molecular weight polymers such as poly (α-olefin)s play a key role as drag-reducing agents which are commonly used in pipeline industry. Heterogeneous Ziegler-Natta catalyst system of MgCl 2 .nEtOH/TiCl 4 /donor was prepared using a spherical MgCl 2 support and utilized in synthesis of poly(1-hexene)s with a viscosity average molecular weight (M v ) up to 3.5 × 10 3 kDa. The influence of effective parameters including Al/Ti ratio, polymerization temperature, monomer concentration, effect of alkylaluminus type on the productivity, and molecular weight of the products was evaluated. It was suggested that the reactivity of the Al-R group and the bulkiness of the cocatalyst were correlated to the performance of the Ziegler-Natta catalyst at different polymerization time and temperatures, affecting the catalyst activity and M v of polymers. Moreover, bulk polymerization method leads to higher viscosity average molecular weights, revealing the remarkable effect of polymerization method on the chain microstructure. Fourier transform infrared, 13 C Nuclear magnetic resonance spectra, and DSC thermogram of the prepared polymers confirmed the formation of poly(1-hexene). The properties of the polymers measured by vortex test showed that these polymers could be used as a drag-reducing agent. Drag-reducing behaviors of the polymers exhibited a dependence on the M v of the obtained polymers that was changed by variation in polymerization parameters.

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“…According to the catalyst activities listed in Table , it can be deduced that although the antioxidant mixture has synergetic effect on the activity of metallocene catalyst, it has an adverse effect on the iron and hybrid catalysts activities and decreases the catalyst activities to lower than the activity of samples without antioxidants. This could be attributed to the difference between the behaviors of both the catalysts regarding their activities and thermal properties which were studied before …”

Section: Resultsmentioning

confidence: 99%

Effect of different additives and their mixtures on thermal stability of polyethylene synthesized using iron and titanocene hybrid catalysts

Fayegh

Ahmadjo

Mortazavi

2017

J of Applied Polymer Sci

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Traditionally, additives are introduced into a polymer matrix via extrusion process which consumes a high amount of energy. In this study, the use of different additives including antioxidants for the in‐reactor stabilization of polyethylene has been investigated in order to provide an energy saving system. Particular attention was dedicated to the efficiency of antioxidant influencing the catalysts activity and properties of polymers. The effect of the addition of Irganox 1330 and Irgafos 168 antioxidants and zinc stearate on the activities of metallocene, post‐metallocene, and their supported hybrid were studied. In addition, the effect of different additives on the thermal characteristics of the synthesized polymers and oxidative induction time (OIT) was evaluated. Our polymerization results exhibited that the factors such as chemical structure of antioxidant and its steric hindrance, type of catalysts, and their hybrid could affect the catalyst performance and OIT contents. The use of antioxidants mixture and hybrid of catalysts is a way that can increase oxidation resistance of polymers considerably. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45482.

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Thermal Behavior of Polyethylene Reactor Alloys Polymerized by Ziegler–Natta/Late Transition Metal Hybrid Catalyst

Cited by 14 publications

References 55 publications

Characteristics of linear/branched polyethylene reactor blends synthesized by metallocene/late transitional metal hybrid catalysts

Characteristics of linear/branched polyethylene reactor blends synthesized by metallocene/late transitional metal hybrid catalysts

Preparation of ultra high molecular weight amorphous poly(1-hexene) by a Ziegler-Natta catalyst

Effect of different additives and their mixtures on thermal stability of polyethylene synthesized using iron and titanocene hybrid catalysts

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